1. Field of the Invention
The present invention relates to an ink jet recording apparatus and, more particularly, to an ink jet recording apparatus provided with a function to perform such recording as to eliminate both top and bottom blank portions of a recording material.
Note here that in the following description a term xe2x80x9crecordxe2x80x9d (xe2x80x9cprintxe2x80x9d in some cases) is supposed to mean generally forming an image, a design, a pattern, etc. on a printing medium or processing the medium irrespective of whether significant information such as a character or a graphic or insignificant information is made up and also irrespective of whether the information is so visualized as to be perceptible to a human with the sense of sight.
Furthermore, a xe2x80x9crecording sheetxe2x80x9d as a recording medium is supposed to mean not only a paper used in a typical printer but also a wide variety of media capable of receiving ink such as a cloth, a plastic film, glass, a ceramic member, wood, leather, etc.
Furthermore, xe2x80x9cinkxe2x80x9d (xe2x80x9cliquidxe2x80x9d in some cases) should be interpreted broadly as in the case of the above-mentioned definition of the term xe2x80x9crecordxe2x80x9d and, therefore, is supposed to refer to a liquid that can be applied onto a recording sheet so as to form an image, a design, a pattern, etc. or to process the recording sheet or also to treat ink (for example, coagulate or make insoluble, a color material contained in the ink) applied on the recording sheet.
2. Description of the Related Art
FIG. 21 is a schematic configuration diagram of a generic ink jet recording apparatus. This ink jet recording apparatus comprises a sheet feeding section for feeding recording sheets one by one, a conveying section for conveying a recording sheet fed from the sheet feeding section to a recording section, the recording section including a recording head 206 for ejecting ink, in recording, to the recording sheet conveyed by this conveying section, and a sheet discharging section including a sheet discharging roller 207 for discharging the recording sheet conveyed to the recording section to the outside of the apparatus.
The sheet feeding section has a sheet loading portion 200 on which recording sheets 201 are loaded and a sheet feeding roller 202 for separately conveying recording sheets 201 one by one from this sheet loading portion 200. The conveying section has an LF roller 203 for feeding the recording sheet 201 separately conveyed by the sheet feeding roller 202 to the recording section and a platen 204 disposed opposite to the recording head 206 for regulating a position of the recording sheet 201 at a recording position of the recording head 206. The recording head 206 has a row consisting of a plurality of nozzles arranged in a direction in which the recording sheet 201 is conveyed so that these nozzles may eject out ink therefrom.
In this ink jet recording apparatus, the sheet feeding roller 202 rotates to feed out the recording sheets 201 from the sheet loading portion 200 one by one. The thus fed out recording sheet 201 arrives at the LF roller 203 and is regulated at its top or leading edge there and then fed out by the LF roller 203 onto the platen 204. When the top of the recording sheet 201 thus fed out onto the platen 204 arrives at a predetermined position, the recording head 206 starts recording. When it is finished being printed by the recording head 206, the recording sheet 201 reaches the sheet discharging roller 207 and then is discharged out of the apparatus by this sheet discharging roller 207.
In ordinary recording, a blank region is provided at the edges (four sides including the top and bottom) of the recording sheet 201, whereas recently data can be recorded with no blank region as in the case of such printing with no blank region on each of the four sides as to be generally conducted in the service of printing out an image recorded on a photo film.
Such blank-less recording can be implemented by supplying image data having a size a little larger than that of a recording sheet so that the data, when recorded, may overflow slightly from each of the four edges of the recording sheet. If this blank-less recording is performed using such a platen construction as shown in FIG. 21, ink ejected out of the recording sheet sticks to the surface of the platen, thus contaminating the recording sheet
To solve this problem of recording sheet contamination, there is proposed such a design that a large hole is provided all over such a region on the platen surface as to be opposite the nozzle row of the recording head. In this case, the dumped extra ink ejected out in top-and-bottom blank-less recording is collected through that hole, thus preventing the ink from sticking to the platen surface.
Besides the above, such a recording apparatus is proposed that a first hole is provided in a portion of the platen surface which is opposite to a part in the downstream side of the nozzle row of the recording head so that this downstream side part may be used to perform top blank-less recording on a recording sheet and a second hole is provided in a portion of the platen surface which is disposed opposite to a part in the upstream side of the nozzle row of the recording head so that this upstream side part may be used to perform bottom blank-less recording on this record material. In this case, the ink dumped in top blank-less and bottom blank-less recording is received through the first and second holes, respectively.
Furthermore, a recording apparatus is proposed such that a central hole is provided in a recording-sheet conveying direction at the center of such a flat top portion of the platen surface as to support a recording sheet so that nozzles of the row which is disposed opposite to this central hole may be used in top-and-bottom blank-less recording on the recording sheet. In this case, the ink dumped in the top-and-bottom blank-less recording is received through the central hole.
The above-mentioned conventional constructions capable of blank-less recording, however, have the following problems.
The construction that has a large hole all over the region on the platen surface opposite the nozzle row of the recording head has a problem of so-called paper jamming occurring when the top of a recording sheet conveyed by the conveying roller hits the wall of the hole. In addition, since the large hole is provided in the platen surface, a reference face to regulate the position of the recording sheet on the platen is restricted in size by that large hole and cannot securely support the recording sheet. This results in a problem of an indefinite distance between the recording head and the recording sheet, thus giving rise to a problem of deterioration in recording quality.
The construction provided with the first and second holes in the platen surface and that provided with the central hole therein both have a smaller size of the holes themselves and so do not suffer from the problem of paper jamming or deterioration in recording quality. A recording apparatus having such construction, however, cannot employ recording heads that are different in position or length of the nozzles in the direction in which the recording sheet is conveyed. To use such a recording head, it is necessary to provide a preliminary ejection outlet in the platen at a different position corresponding to the recording head, so that one more platen must be provided as a different part. Therefore, platen parts cannot commonly be used for the recording heads different in position or length of the nozzles, thus giving rise to a disadvantage in manufacturing costs.
It is an object of the present invention to provide a low-cost ink jet recording apparatus that can avoid paper jamming and deterioration in recording quality.
It is another object of the present invention to provide an ink jet recording apparatus that comprises head mounting means for mounting thereon a first recording head having a row of nozzles in which a plurality of nozzles are provided in a predetermined direction, to eject ink from at least some of said row of nozzles in order to record data on a recording sheet conveyed in said predetermined direction and a platen arranged opposite to said head mounting means, for regulating a position of said recording sheet, in which said first recording head can be replaced by a second recording head different from said first recording head in position or length in said predetermined direction of said row of nozzles and said platen has such a preliminary ejection outlet common to said first and second recording heads as to guide ink ejected from said part of said row of nozzles.